Mélofée: Researchers Uncover New Linux Malware Linked to Chinese APT Groups

Mar 29, 2023Ravie LakshmananLinux / Cyber Threat

An unknown Chinese state-sponsored hacking group has been linked
to a novel piece of malware aimed at Linux servers.

French cybersecurity firm ExaTrack, which found three samples of
the previously documented malicious software that date back to
early 2022, dubbed it Mélofée.

One of the artifacts is designed to drop a kernel-mode rootkit
that’s based on an open source project referred to as Reptile^[1].

“According to the vermagic metadata, it is compiled for a kernel
version 5.10.112-108.499.amzn2.x86_64,” the company said^[2] in a report. “The
rootkit has a limited set of features, mainly installing a hook
designed for hiding itself.”

Both the implant and the rootkit are said to be deployed using
shell commands that download an installer and a custom binary
package from a remote server.

The installer takes the binary package as an argument and then
extracts the rootkit as well as a server implant module that’s
currently under active development.

Mélofée’s features are no different from other backdoors of its
kind, enabling it to contact a remote server and receive
instructions that allow it to carry out file operations, create
sockets, launch a shell, and execute arbitrary commands.

The malware’s ties to China come from infrastructure overlaps
with groups such as APT41^[3]
(aka Winnti^[4]) and Earth Berberoka^[5]
(aka GamblingPuppet^[6]).

Earth Berberoka is the name given to a state-sponsored actor
chiefly targeting gambling websites in China since at least 2020
using multi-platform malware like HelloBot and Pupy RAT^[7].

According to Trend Micro, some samples of the Python-based Pupy
RAT have been concealed using the Reptile rootkit.

Also discovered by ExaTrack is another implant codenamed
AlienReverse, which shares code similarities with Mélofée and makes
use of publicly-available tools like EarthWorm^[9] and socks_proxy^[10].

“The Mélofée implant family is another tool in the arsenal of
Chinese state sponsored attackers, which show constant innovation
and development,” the company said.

“The capabilities offered by Mélofée are relatively simple, but
may enable adversaries to conduct their attacks under the radar.
These implants were not widely seen, showing that the attackers are
likely limiting its usage to high value targets.”